P1516: THE CLINICAL IMPACT OF IMMUNOGLOBULIN REPLACEMENT THERAPY ON SEVERE BACTERIAL INFECTION IN PATIENTS WITH HYPOGAMMAGLOBULINEMIA SECONDARY TO HEMATOLOGIC MALIGNANCIES: A JAPANESE CLAIMS DATABASE STUDY
Authors: Keichiro Mihara, Takakazu Kawase, Takahiko Miyama, Katsuhiko Iwasaki, Ayako Shoji, Masayuki Matsumaru
Journal: HemaSphere (2023)

Topic: 30. Infections in hematology (incl. supportive care/therapy) Background: Secondary hypogammaglobulinemia (HGG) is a risk factor for infectious events and known to be induced by hematologic malignancies (HMs) and their treatments, such as B-cell–targeted agents and hematopoietic stem cell transplantation (HSCT). Clinical guidelines on HMs recommend immunoglobulin replacement therapy (IgRT) for patients with HGG and/or a history of repeated or severe infection. In Japan, intravenous immunoglobulins and a subcutaneous immunoglobulin are available. However, the use and effectiveness of IgRT in real-world clinical practice in Japan is not sufficiently understood. Aims: To investigate the clinical impact of IgRT on severe bacterial infections (SBIs) in patients with secondary HGG. Methods: We performed a retrospective study with Japanese claims data provided by Medical Data Vision Co., Ltd. (Tokyo, Japan). Individuals were enrolled as users of IgRT for HGG if they met all of the following criteria: 1) diagnosed with an HM and HGG during the study period (May 2010 – March 2021); 2) prescribed IgRT both after the first diagnosis of an HM and after that of HGG (the first prescription date was the index date); 3) had more than 1 record both 12 months before and 12 months after the index date (baseline and follow-up, respectively); 4) received more than 1 course of IgRT in the follow-up period; 5) aged 16 years or older at the index date; and 6) started IgRT at the adequate dose (> 5 g/month). Patients diagnosed with immunodeficiency, human immunodeficiency virus infection, or other diseases for which IgRT can be used in Japan were excluded. SBI was defined as hospitalization with intravenous antibiotic treatments, and SBI incidence, as the number of the hospitalizations. We compared SBI incidence per person-year between the 12-month baseline and follow-up periods (primary endpoint) and confirmed the results by performing the same comparison after changing the length of both periods (secondary endpoints). Results: We enrolled 1621 patients with a median age of 60.0 years. The diagnosis was non-Hodgkin’s lymphoma in 37.9% of patients and multiple myeloma in 17.7%. Other medical histories were anti-CD20 antibody (22.8%) and anti-CD38 antibody (3.8%); 24.4% of patients had received HSCT. The SBI incidence was significantly lower in the follow-up period than in the baseline period (2.3 vs. 0.9, respectively; p < 0.001), and a similar result was obtained when 3 months was used as the length of the baseline and follow-up periods (3.2 vs. 0.9, respectively; p < 0.001) and in subgroup analyses classified by type of B-cell–targeted agent, history of HSCT, and IgRT dose in the 3 months after the index date. Summary/Conclusion: The SBI incidence is lower after the start of IgRT regardless of the length and definition of the observation period. The study has some limitations related to the use of the hospital-based claims database, so results need to be confirmed. Given these results, IgRT is expected to decrease the incidence of SBI in patients with HGG treated in real-world clinical practice in Japan. Keywords: Infection, Immunodeficiency, Immunoglobulin